At present, in the field of wireless networks, the wireless local area network (WLAN) develops rapidly, the demand for WLAN coverage is growing, WLAN is applied more widely, and deployment density of the WLAN is also increasing rapidly.
The IEEE 802.11 technology defines a Basic Service Set (BSS) consisting of one Access Point (AP) and a plurality of Stations (STAs) associated with the AP. Multiple stations can share the same wireless channel by using a mechanism of Carrier Sense Multiple Access with collision avoidance (CSMA/CA). The working principle of the CSMA/CA is described as follows. A transmitting device first detects whether a channel is idle, and if the channel is detected to be idle, the data is transmitted after waiting for a random period of time. If a receiving station receives the frame correctly, the receiving station transmits an acknowledgment (ACK) frame to the transmitting station after waiting for a period of time. The transmitting station, upon receiving the ACK frame, determines that the data is correctly transmitted.
In the CAMA/CA technology, the station uses a physical carrier channel idle state detection technology (e.g., Clear Channel Assessment (CCA)) to detect whether the channel is idle before transmitting a radio frame. Specifically, the station detects a signal interference level of a physical carrier channel within a period of time. When the signal interference level is higher than a standard defined fixed threshold value, the state of the carrier channel is considered busy; otherwise, i.e., when the signal interference level is lower than the fixed threshold value, the status of the carrier channel is considered idle and available.
When the above CSMA/CA technology is used to detect whether the channel is idle, a fixed threshold is used for determination, and the fixed threshold cannot adaptively change along with the WLAN deployment density. As a result, stations cannot raise the probability of transmitting data even when the interference between the stations has decreased, thus affecting the spectrum utilization efficiency.
In order to solve this technical problem, a technical solution has been proposed in the related art that allows to dynamically adjust the threshold value for determining whether the channel is idle according to the signal interference level measurement result of the physical carrier channel within a certain period of time. In this solution, the station is first allowed to set a temporary signal threshold according to the interference level measurement result and the engineering experience. When the distance between the transmitting station and the receiving station is close while the distance between the transmitting station and the interfering station is far, the above temporary signal threshold is increased, thus raising the data transmission probability of the transmitting station. By virtue of this technical solution, for the overall network statistical performance, the average data transmission delay can be reduced and the average spectrum utilization rate can be improved.
With the development of the Multiple Input Multiple Output (MIMO) technology, the MIMO technology is also introduced in the current WLAN system. The MIMO technology supports the transmitting station to transmit data in a directional beamforming technique. The transmitting station can concentrate the transmitted signal energy in a small spatial range, thereby improving transmission performance and transmission distance, and causing very small interference to other stations outside the above spatial range. Since the associated WLAN divides the channel only by frequency, rather than divides the channel by space, when the relevant channel idle detection is performed in the MIMO-WLAN network, the transmitting station stops transmitting data once the channel is detected to be busy. But in fact, the transmitting station using the MIMO technology may be only interfered from other stations in a certain direction. If the transmitting station stops transmitting data in various transmitting directions, data transmission probability of the transmitting station is undoubtedly reduced.